Photoelectric Effect - Example
Most metals have a work function on the order of several electron volts. Copper has a work function of 4.5 eV.
Therefore, the cut-off frequency for light ejecting electrons from copper is:
fcutoff = 4.5 x (1.6 x 10-19 C) x (1 V) / 6.63 x 10-34 J-sec